Public Safety Advocate: FirstNet Coverage

During the quest to obtain enough nationwide broadband spectrum for public safety, the Public Safety Alliance (PSA) and its member organizations worked industriously to convince members of the U.S. Congress and their staffs, the FCC, and the Executive Branch of the federal government that public safety needed more broadband spectrum than had been assigned to them (10 MHz, 5X5 MHz). The result of this multi-year effort was that Congress listened and in the legislation that created FirstNet, public safety was assigned 20 MHz (10X10 MHz) of spectrum (referred to as Band 14). This spectrum is in the 700-MHz band adjacent to the Public Safety Land Mobile Radio spectrum on one side and Verizon’s 700-MHz spectrum on the other side. It is ideal for longer range and better in-building penetration.

It was always assumed by the public safety community that the winning bidder of the FirstNet RFP would, of course, build out the FirstNet spectrum nationwide. Even with a full 20 MHz of spectrum to which public safety has pre-emptive access, there were still some concerns from a number of us that during an incident contained in a small area served by only one or two cell sectors, there would still be times when the network reached its maximum capacity. When AT&T won the contract and became the partner for FirstNet, it did not specify its build-out plans publicly. However, at the recent Senate Sub-committee, AT&T’s plans for the build-out were presented to those on the committee and picked up by the press. AT&T’s decision is to build out FirstNet spectrum where it is needed for capacity but nowhere else (Urgent Communications report).

This decision is based on AT&T having made all of its existing and future LTE spectrum available with full pre-emption for public safety in addition to the Band 14 spectrum. In most areas of the United States this will result in public safety having access to double or even triple the spectrum and public safety will have full priority access on all of it. AT&T has made the public safety network better overall, I believe, because having access to more spectrum in most areas will mean pre-emption will be required less often, more data and video can be sent and received to and from incidents, and since the devices will all be equipped with all of the AT&T LTE spectrum, users will not have to worry about roaming onto other networks or managing administrative users during an emergency. The network will ensure that the field devices are operating on the best portion of AT&T spectrum for the location and amount of other traffic on the network.

Further, AT&T has stated that as it upgrades its own network, including the deployment of 5G or small-cell technology (mostly in urban areas) the FirstNet network will be upgraded as well. AT&T does not seem to think it will need the FirstNet spectrum except in major metro areas. AT&T may be correct in its assessment but I have to take exception to this vision of where to build out FirstNet’s spectrum.

One of the prime advantages of Band 14 is that it has been categorized as public safety spectrum under FCC part 90 rules and the FCC has permitted, on Band 14 only, LTE devices in the field to run at a power level far greater than typical LTE devices. On the AT&T network, and all of the other commercial LTE networks, the devices in the field transmit at ¼ Watt (250 mW or 24 dB). However, on Band 14 the permitted power level is 1.25 Watts (31 dB), which will make a tremendous difference in rural areas that are, today, sparsely covered with cellular and even less covered with LTE service.

If you equip an emergency response vehicle with a 1.25-Watt modem, use external antennas, and add WiFi to the device, each vehicle becomes a relay for lower-powered devices used in and around the vehicle. Then there is the issue of direct-mode communications. Because Band 14 won’t be built out in all of the coverage area does not mean the devices cannot be equipped with Band 14 to provide better direct-mode coverage if and when LTE comes up with a satisfactory method for direct-mode over LTE. (It is still not clear whether even this power level will be good enough for public safety, but it is better than ¼ of a Watt!)

Coverage Maps

There has been a lot of discussion within the states regarding the coverage maps provided by FirstNet and AT&T. The public can view these maps at FirstNet.com and drill down on them, and they are also included on the portal with access limited to only those within each state who have been authorized. During a state briefing I attended, AT&T said the coverage shown is indoor coverage with a signal level of -98 dB. This has been further clarified by AT&T recently to state that outdoor coverage levels shown on the maps are -110 dB. For a point of reference, I am told by LTE device engineers that you can expect an LTE device to hear down to the -118 dB to -120 dB range. However, in addition to the stated coverage there will be additional losses due to personal attenuation (where the device is placed on a person and how much that impacts the receiver’s capability to hear.)

We are hearing and there have been some press articles claiming the coverage maps do not appear to be realistic in certain areas of the country. It is not clear if the coverage plots have been computer-generated and then verified with drive testing or if they have only been computer-generated. The danger of that is that actual coverage from a given site may vary considerably from the coverage shown on a computer-generated coverage map. Since public safety personnel are sceptics to begin with, when they discover discrepancies between the stated coverage and the actual coverage they experience, they generally end up discounting any of the coverage information provided.

Expectations

However, the public safety community should not expect or demand that coverage offered on day one is the final coverage they will have going forward. First, the contract states that this is a 5-year build-out, followed by another 20 years of upgrades and operation. There will be additions to the coverage during both the build-out and the balance of the contract. This will include increasing the overall network footprint, filling in holes where they exist, and adding faster (5G) small cells in many mainly urban areas.

Once a state opts in there is nothing in the law that requires every public safety agency to join the network. In fact, it will be up to each agency to decide if it wants to join right away, wait until AT&T can prove the coverage in its area is up to par, or in some cases simply not join the network at all. However, not joining the network does not solve the interoperability problem, which was the vision of the network from day one. Being on a different network, with different servers, and devices that might not be capable of Band 14 or the AT&T spectrum will put any department that makes that decision less interoperable with those around them and in the rest of the country.

Working with AT&T

AT&T’s top senior vice president for FirstNet and other executives have all stated they understand they have to earn public safety’s business. The real work begins after a state opts in and AT&T has to work with local jurisdictions to prove it can provide the required coverage and services. At the state meeting I attended, I asked if AT&T would work with agencies, cities, and counties to figure out how to fill in coverage even after a state has opted in and the answer was yes. And there are several other issues AT&T and FirstNet need to consider when planning their Band 14 deployment. The first is that in rural areas, where there are many other federal grants available that can be used for rural broadband and the combination of the Band 14 spectrum, federal and state grants can provide additional rural coverage not only for the public safety community, but also for those in the area who have no access to broadband services. Band 14 would provide longer-range communications for public safety while at the same time providing coverage for the rural population. The result is better communications for public safety, educational, medical, business, and residential users who do not have access now. The last benefit would be that local and even state politicians could brag about extending coverage in their rural areas during the election season.

Conclusions

There is bound to be pushback from the public safety community on the Band 14 build-out. AT&T and FirstNet will have to be upfront and able to explain the rationale behind this. From a network capacity point of view, it makes sense. If public safety has full pre-emption on all AT&T spectrum there are many areas of the country that, today, do not need Band 14. However, I have to wonder if by not committing to building Band 14 out if someone, somewhere, might try to make a case for obtaining access to Band 14 in areas where AT&T does not plan to build. We cannot let this happen because even though it may not be needed today, with the demand for streaming video and other services doubling every year and with new applications and services coming online for public safety, I believe at some point Band 14 will end up with nationwide coverage.